/Engine/Plugins/Experimental/AnimNext/Source/AnimNext/Public/Param/ParamStack.h
Stack of parameter layers. Acts as an associative container - allows retrieval of parameter calues (by ID) that have been pushed onto the stack in 'layers'. Parameter values (and notably types) on higher stack layers override those on lower layers. Older values and types are restored when a layer is popped. Parameter values, once pushed, can be overridden by subsequent layers, but they cannot be removed until the layer that initially introduces the parameter is popped.
struct FParamStack